The present invention relates to the killing of microorganisms on food items, without degrading the food items. The invention finds particular application in conjunction with almonds and will be described with particular reference thereto. However, it is to be appreciated, the invention will also find application in conjunction with other types of nuts, seeds, dehydrated fruits, and other agricultural products.
To promote the growth of agricultural products, fertilizer is typically added to the soil. Manure, a commonly used fertilizer, can carry human pathogens, such as Salmonella, E-coli, and Listeria. When food items come into contact with the soil during harvesting, or with equipment that has contacted the soil, the food items can pick up the human pathogens on their surface. As the harvested food items are gathered together, the pathogens can be passed from surface to surface by direct contact.
When harvesting almonds, for example, it is common to shake the trees dropping the almonds (in their shells and husks) to the ground. The almonds are then collected from the ground. In a first operation, the husks are removed from the almonds, leaving the almonds in their shells. Some almonds are sold in their shells, and others are deshelled prior to packaging. The removed husks would be expected to be the carriers of any human pathogens picked up from the soil. Even after husking, the shell provides a pathogen impermeable package for the nutmeat. Conventional, mechanical shelling operations raise a significant amount of dust, sending dust-sized portions of the shell and any pathogens which might be thereon airborne.
Subsequently, the shelled nutmeats undergo various sorting operations. Some of the nutmeats are cooked, which would also be expected to kill any surface pathogens. Other nutmeats are packaged and sold raw. Although the chances of human pathogens being present on the packaged nutmeats might appear relatively remote, there have been recent recalls of almonds for Salmonella contamination.
One solution to the contamination problem is found in the present assignee's U.S. Pat. Nos. 5,460,845 and 5,535,667. These patents describe a batch process in which almonds and other food items are exposed to hydrogen peroxide vapor in a vacuum chamber for periods of about a half hour to one hour. These patents also describe limited kill rates at somewhat shorter periods of exposure at atmospheric pressure.
Although effective, such batch processing techniques are not readily compatible with modern processing plants in which each processing line processes about 10,000 kilograms of food product per hour or more.
The present invention overcomes the above-referenced problems and others.